Opacity of an object in 2.8
The setup is very basic. One thing to note is that I've used Wireframe modifier with second material.
Material
Just a mix between Transparent and Emission which is added for colorization and &quot;nicer&quot; visibility.

Material setup
First slot is above material for transparent object, second is for wireframe.
Most important thing here is to set Blend Mode Type as Alpha Blend.

Modifier
In Wireframe modifier set Material offset to 1 to be able to use material from second slot. Also set wireframe Offset to -1. It will hide wireframe object in main object.
Don't forget to uncheck &quot;Replace Original&quot;, or else the low transparency would be replaced by wireframe. We want the mesh to have wireframe with the transparency, not just the wireframe.